This invention is directed to providing an improved drain pipe, and particularly to providing an improved drain pipe of the type used in the drainage of soil and the transportation of surface water by gravity for agricultural, septic, residential, civil construction, or recreational purposes. Typical product sold to residential end users is nominally four inches in diameter and sold in ten foot straight lengths or in rolls of 50 to 300 feet in length. Typically, the color is black and the material is high density polyethylene (HDPE). The plastic drain pipe is corrugated on the exterior and may or may not have a smooth interior wall. Both straight lengths and rolls of the corrugated pipe are not collapsible, and as a result are bulky. Some types of corrugated pipe require connectors to join pieces or elbows to cause the pipe to hold a curved position. Pipe sold in rolls tends to retain a memory making it difficult to place in a trench without elbows or weighting the pipe sections down with ballast such as rocks or a building block. Both the straight lengths and rolled corrugated pipe need to be cut to length. Corrugated pipe sections that are adapted to connect with adjacent sections often utilize proprietary connecting configurations and are rendered inoperable with pipe sections manufactured by other suppliers.
In the field of gutter downspouts, collapsible corrugated tubing has been utilized by Gutter. World, Inc. as reflected in U.S. Pat. Nos. 5,813,701; 5,915,735; 6,041,825; and 6,223,777. These downspout extensions have male and female rectangular end sections to connect with gutter downspouts and adjacent extensions. In addition, the corrugated collapsible downspout extension pipes have only been used in relatively short lengths, approximately six to eight feet long when fully extended, have utilized thick wall corrugations, and have utilized a profile that did not optimize either the collapse ratio or the bend radius of the product. It is believed that the downspout extension products have only been sold in a straight collapsed configuration which, with non-collapsible end sections, results in a longitudinal product between two and three feet in overall length.
Gutter World, Inc. has also manufactured a rectangular profile collapsible gutter spout tubing in lengths of less than about two feet when fully extended. Although this rectangular product approximates some measurements in its straight walled corrugations to the annular corrugations of the present invention, rectangular corrugated products have inherently irregular wall thicknesses. When fabricated on a corrugator, the midpoints of straight walls are thicker than the walls near corners, and thus the entire tubing must be made with relatively thick walls to ensure adequate coverage in the corner areas. This leads to thicker midpoints of walls in comparison to the corners, causing the resulting rectangular product to collapse irregularly.
Most other collapsible corrugated tubing has been constructed for medical uses in smaller diameter sizes such as about 1 to 1.5 inches. These tubings are much smaller and lighter than drainage tubing, which typically has a diameter at least about 3 inches and must possess some rigidity so that it is not crushed when buried in a trench. Due to the relatively small sizes and thin walls of these prior collapsible tubes, it has been possible to work with small tubes even when they were not optimized for portability and ease of manipulation.